Injection systems of motor vehicles require intelligent adaptation methods in order to meet the requirements for the course of combustion/emissions/acoustics. In this respect, the system performance in the new state as well as in aged systems is highly significant.
Such adaptation methods are known. For example, a so-called MFMA (minimum fuel mass adaptation) method is known, in which the deviations in the actual and setpoint injection quantities are determined in the minimum quantity range (<3 mg) during the service life of the motor vehicle on the basis of changes in engine speed, and are constantly adapted. According to this method, small quantities of fuel are injected into a cylinder in overrun phases, in which injection normally does not occur, and the change in engine speed is used to calculate the associated injection quantity by reference to models. The correction variables are stored in program maps, on an injector-specific basis for the tested minimum quantities. Such a method is described in DE 102 57 686 A1.
New vehicle functions, such as the sailing mode, for example, pose considerable limitations for the activation of the MFMA method, however, since fewer and fewer overrun phases occur in these cases. As a result, this correction method is activated to a lesser and lesser extent in vehicles of this type, and therefore an adaptation of an injection quantity ultimately no longer takes place. In addition, the application thereof requires a relatively great amount of effort given that there are numerous variations of transmission/clutch.